Ochnaflavone, Naturally Occurring Biflavonoid, Inhibits Phospholipase A_2 Dependent Phosphatidylethanolamine Degradation in a CCl_4-Induced Rat Liver Microsome(Biochemistry)

This study investigated the protective effects of a group IIA secretory phospholipase A_2 (sPLA_2-IIA) inhibitor, ochnaflavone, on the progression of carbon tetrachloride (CCl_4)-induced acute liver injury in rat liver microsomes in vitro. When rat liver was incubated at 37℃ in the presence of CCl_4, the level of phosphatidylethanolamine (PE) degradation increased markedly compared with the control. The rat 14 kDa platelet PLA_2 antibody, R377, suppressed the degradation of PE. Pretreating the microsome with ochnaflavone (2-16 μM) reduced the level of PE degradation in a dose dependent manner. In addition, p-bromophenacy bromide (p-BPB), which is a PLA_2 inhibitor, also inhibited PE degradation. However, the inhibitory activity was weaker than that of ochnaflavone. Further investigation showed that ochnaflavone not only inhibited the purified rat platelet sPLA_2 activity in a dose dependent manner with an IC_<50> value of 3.45 μM, when arachidonyl PE was used as a substrate, but also inhibited lipid peroxidation in a dose dependent manner with an IC_<50> value of 7.16μM. This result suggests that ochnaflavone prevents the progression of CCl_4-induced PE hydrolysis by inhibiting the endogenous sPLA_2 activity.